On Mon, 07 Mar 2011 16:31:32 -0800, Jeff Liebermann wrote:
On Mon, 7 Mar 2011 19:57:03 +0000 (UTC), Meat Plow
wrote:
On Mon, 07 Mar 2011 10:48:00 -0800, William Sommerwerck wrote:
Can anybody comment on lip sync?
On Comcast a few channels have imperfect lip sync. As to why -- I
don't know.
I've only had a small problem with Discovery HD. Once in a while I get
some pixelation. Something you would expect with a less than adequate
signal. But that's not the case. And the cable company can't explain it.
This might add fuel to the fire. Note that this is from a cable
industry insider, published in a CATV industry journal:
http://www.cedmagazine.com/articles/...orner-can-you-
hear-me.aspx
Digital television has brought the scourge of lip sync errors.
Video signals and aural signals require vastly different processing,
which results in different amounts of processing time. Unless
appropriate additional artificial delay is added, the sound and the
video will end up out of synchronization. This difference can
accumulate if multiple conversions take place in the path from the
original source to the final display site. Ive seen lip sync
discrepancies that were so bad, it appeared that the characters were
speaking another language and that the speech I was hearing was
dubbed in. The problem is so pervasive that my sound system comes
with a delay adjustment so that I can manually compensate at home.
That would be a reasonable solution if the delay was constant from
channel to channel, or even from program to program on the same
channel. But it is not.
On the home front, I've seen sound sync fall apart when ripping and
transcoding content from a DVD to some other video protocol. There are
tweaks for the problem, such as VLC which allows you to speed up or slow
down the audio using the "f" and "g" keys. You can also "desync" the
video and audio for a fixed user settable delay. The problem is that
controlling the sync seems to be too much of challenge for broadcasters
and cable companies. To make things worse, it seems (to me) that
different ATSC decoders have varying delays. It's suppose to be
controlled to between +15 and -45 msec but I'm beginning to have my
doubts:
http://www.pixelinstruments.tv/articles.htm
http://www.pixelinstruments.tv/articles5.htm (Lots more on audio sync
on the above URL).
Incidentally, if you also happen to notice that cable video doth suck,
you might find this article, from the same issue, rather illuminating:
http://www.cedmagazine.com/articles/...presto-change-
o.aspx
Bookmarked for perusal tomorrow morning after coffee.
--
Live Fast, Die Young and Leave a Pretty Corpse